7 (b.b.) TME = PE + KE

Think about the pass thrown by the quarterback. A football thrown by a quarterback has mechanical energy. So does a moving car or a trophy on a shelf. The form of energy associated with the position and motion of an object is called mechanical energy.An object’s mechanical energy is a combination of its potential energy and kinetic energy. For example, a thrown football’s mechanical energy is a combination of its position above the ground and its motion. Sometimes an object’s mechanical energy is its kinetic energy or potential energy only. A car moving along a flat road possesses kinetic energy only. A trophy resting on a shelf has gravitational potential energy only. But both have mechanical energy.You can find an object’s mechanical energy by adding the object’s kinetic energy and potential energy.

You can use this formula to find the mechanical energy of the football in Figure 5. The football has 32 joules of potential energy due to its position above the ground. It also has 45 joules of kinetic energy due to its motion. The total mechanical energy of the football is 32 joules + 45 joules, or 77 joules.